The use of vapor recovery fuel dispensing nozzles is becoming increasingly more prevalent because of environmental concerns and to meet environmental regulations. These nozzles are of several different types, but the nozzles for use in a vacuum assist vapor recovery system appear to be the nozzles of choice in most instances.
In vacuum assist vapor recovery systems, a vacuum pump or other positive flow inducing device creates a vacuum in the vapor recovery passage in the spout of the nozzle to draw vapor from the vehicle tank, through the nozzle and dispenser and to deliver the vapor into the underground tank from which the fuel is withdrawn by the dispenser. To avoid unduly pressurizing the underground tank, it is important to control the rate or volume of vapor recovered in proportion to the rate or volume of the fuel dispensed.
Various vapor recovery volume control systems have been proposed, but all have presented certain disadvantages or deficiencies. Some of these proposed systems have included fuel flow rate sensing means in the fuel line from the underground tank to the dispenser and some vapor flow control means in the vapor line from the dispenser to the underground tank. Examples of such systems are disclosed in U.S. Pat. Nos. 5,150,742; 5,040,577; 4,202,385; and 3,826,291. The systems disclosed in U.S. Pat. Nos. 5,150,742 and 4,202,385 disclose a hydraulic motor or turbine located in the fuel line and an impeller in the vapor recovery line for recovering the vapor. The hydraulic motor or turbine is connected to the impeller to drive the impeller when the motor or turbine is driven by the fuel dispensed. The system of the U.S. Pat. No. 3,826,291 drives the vapor recovery impeller from the shaft of the meter which records the amount of fuel dispensed.
Another type of vapor flow control system which has been proposed locates the vapor flow control in the delivery hose from the dispenser to the nozzle. Examples of this type of system are disclosed in U.S. Pat. Nos. 5,217,051; 4,068,687; and 3,016,928, in which rotary turbines and impellers are provided in the fuel delivery conduit and in the vapor recovery conduit of the hose.
Finally, it has been proposed to control vapor recovery from the nozzle by having a fuel flow responsive turbine drive a vapor recovery impeller. Incorporating such rotary elements in the nozzle imposes certain difficulties and maintenance problems and are not designed for use with vacuum assist vapor recovery systems.